STAINLESS STEEL GLOCK GUIDE ROD Recommended usage of either an ISMI recoil spring in a corresponding correct weight for your pistol. In most cases 13-17 lbs. ZEV Guide Rods are NOT Compatible with Glock® Factory Guide Rod Springs. If you plan to use this Guiderod with a Generation 4 model Glock® you must also use a Generation 4 reducer (RDC-4G-SS-DLC)